Engine valve actuator assemblies for engines such as an internal combustion engine on a motor vehicle typically have a roller finger follower that contacts an engine valve and is pivotable in response to cam motion to lift the valve. A typical roller finger follower can be replaced by a hydraulically controlled switchable roller finger follower (“SRFF”). A hydraulically controlled SRFF, which is also referred to herein as a hydraulic lift assembly, can provide two distinct engine valve lifts. Hydraulic control of the SRFF may be designed to achieve a low lift and a high lift of the engine valve or may be designed such that a low lift is zero lift, or results in valve deactivation. An alternative hydraulic lift assembly can include hydraulically controlled switchable hydraulic lifter valves that provide two levels of engine valve lift through a push rod, as is known by those skilled in the art.
Traditionally, such variations in engine valve lift have been achieved by using a cylinder head that has a complex system of fluid supply passages that enable pressurized fluid to communicate with the hydraulic lift assemblies, which are supported in the cylinder head. Cylinder heads with such an integrated hydraulic system are necessarily specific to each engine family and entail numerous production steps such as casting, boring, and finishing the network of channels provided in the cylinder head.
U.S. Pat. No. 6,584,951 issued Jul. 1, 2003 to Patel, et. al and commonly assigned to General Motors Corporation, discloses an engine assembly that requires a separate individual hydraulic circuit module for each engine cylinder which achieves selective deactivation of each cylinder in accordance with the hydraulic controls provided within the cylinder module associated with the cylinder. The cylinder modules of the '951 patent utilize a solenoid valve to selectively block oil flow from a flow channel to an exit port of the module and thereby build oil pressure in the flow channel and in lifter openings of each collapsible hydraulic lifter valve associated with each cylinder. The oil pressure actuates the collapsible lifters to enable cylinder deactivation. The solenoid valve can also be controlled to permit the flow, thus causing the hydraulic lift assembly to cause reciprocal lifting and lowering (i.e., opening and closing) of the engine valve (i.e., actuating the cylinder). Thus, each solenoid valve acts as a two-way on/off valve.